Carrier telegraph circuits



I B. P. HAMILTON CARRIER TELEGRAPH CIRGUIT'S Filed 001;. 21. 1 920 2Sheets-Sheet 1- m. 2', 1 23. 1,%&

B. .P. HAMILTON CARRIER TELEGRAPH CIRCUITS Filed 00f. 21, 1920 2sheets-sheet 2 MW 651 45 @Z 12 6g ME in? r1 INVEN'EOR ATTORNEY iFatentedGot 2, 11 923..

UNHTETD. STATES insane saranr or ies.

BAXTER 1P. HAMILTON, OF BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A COBPGRATI ON OF NEW YORK.

CARRIER TELEGRAPH oraourrs.

Application filed October 1920. Serial No. 418,486.

To all whom it may concern;

Be it known that I, BAXTER P. HAMILTON, residing at Brooklyn, in thecounty of Kings and State of New York, have invented certainImprovements in Carrier Telegraph Circuits, of which the following is .aspecification. A

This invention relates to signaling systems, and more particularlytosystems in which telegraph signals are transmitted by means of carriercurrents.

One of the objects of this invention is to provide a repeater apparatusfor carrier telegraph systems, said repeater apparatus being soarrangedthat a local subscribers circuit or loop may be associated therewith forthe purpose of transmitting signals to and receiving signals from therepeater apparatus. 4

Another object of the invention ,is to pro vide means whereby asubscribers loop will be associated with the repeater apparatus andrepeater telegraph system in such a manner that the loop'will operatefor the transmission of signals to and from the re' peater upon a halfduplex basis. Another ob'ect of the invention is to provide means wereby a subscribers loop will be associated with the repeater apparatusand repeater telegraph system in such a manner that the loop willoperate for the transmission of signals to and fromthe repeater upon afull duplex basis.

Other and further objects of the invention will be clear from thefollowing description when read in connection with the accompanyingdrawings, Figures 1, 2, and 3 of which illustrate circuit diagramsembody ing a number of difl'erent formsot the invention, and Figs. 4 and5 otwhich show the detailed circuit arrangement of the carriertransmitting and receiving apparatus used in connection with therepeater.

Referring to Fig. l, M-LE and MLW designate transmission line sectionsover which carrier currents may be transmitted.

' A transmitting circuit TLE and a receiving circuit RLE are associatedwith the main line section MLE through a balanced transformer 10, anartificial line and network, MNE, being provided for balancing the mainline circuit. For. the same purpose transmitting circuit TLW andreceiving circuit- RL W are associated with the main line IVILW through*abalanced transformer 10 and balancing network MNW. A plurality ofcarrier channels may be associated with each of the transmitting andreceiving circuits above described for multiplex work.

For purposes of illustration, a single channel is shown associated witheach circuit; thus a transmitting channel'- associated withthe circuit'l'LE is illustrated as comprising a transmitting amplifier TAE, towhich an oscillator (1E may be connected under certain circumstances asmore fully explainedhereinafter. A similar transmittin amplifier TAW andoscillator GW are s ownas being associated with the circuit RLW. Theamplifying arrangements above described may be of any well-known form,such as, -for example, vacuum tube amplifiers. The genera-tors may alsobe of any known character adapted to enerate a carrier frequency, butare preferably vacuum tube oscillators. A typical arrangement ofoscillator and amplifier is illustrated in Fig. 4. In practice, when theapparatus is used as a through repeater, the generator is unnecessary,and will be disconnected from the amplifier at the points indicated bythe crosses. The filament of the amplifying tube will, in such case,have its circuit completed to battery directly through a resistance(indicated in dotted lines), which is equal to the resistance of thefilament of the oscillating tube GE.

A receiving channel, comprisin a receiying amplifier lZt-AE, detectorDE, and receiving relay RE, is shown as being associated with thereceiving circuit RLE. A simlar receiving arrangement, comprising anamplifier.RACW, detector DW, and receiving relay 'RW, is shownassociated witlr the receiving circuit RLW. The amplifiers RAE and RAWmav be of any well-known type: for example, vacuum tube amplifiershaving the construction illustrated in Fig. 5.

The detectors, likewise, may be of any wellknown character, but arepreferably vacuum tube detectors, such asillustrated at DE in Fig. 5.The receiving relay is preferably a polar'relay, and, in order that itmay operate upon an alternating current. basis, the polar relay isconnected to the out-put circuit of the detector through a transformer11, as indicated in Fig. 5.

In order that the transmitting and receiving channels may be utilizedfor through repeating, the transmitting channel of each line is directlyconnected to the receiving so l - channel of. the opposite line; forexample, a

conductor 12 interconnects the out-put circuit of the. receivingamplifier 'ItAlV, and the in-put circuit of the transnutting amplifierTAE; likewise, a conductor 13 di rectly connects the out-put circuit ofthe re-- ceiving amplifier RAE and the in-put circuit of thetransmitting amplifier TAE. The manner in which the ci-rcui-t 12 isassociated with the in-put circuit of the ampli Q fier TAE isindicatedin Fig. 4:, and the manner in which the circuit 12-is associated withthe out-putIc-ircuit of the receiving am:

, plifie r RAW will be understood from inspection of the connection ofthe circuit 13 to the receiving amplifier RAE, illustrated iii-Fig. 5.When the amplifiers of the transmitting and receiving channels are thusconnected, the amplifier of the receiving channel works directly intotheamplifier of the transmitting channel, and the carrier sig nals will berepeated at carrier frequency.

'In order that a local subscribers loop L may be associated with therepeater apparatus for transmitting and receiving signals, a jack J isprovided, in which the plug P of the loop may be inserted. The loopconnection leading from jack J is balanced by means of a balancingcircuit N, and three polar relays, PE, and PW, are so associated withthe loop that onewinding of each relay is included in the loopconnection battery lead of one polarity, while the junct the normalcontact of the relay tion point 16 of the windings in the loop andbalancing circuits is connected through a battery lead of theopposite-polarity over PW" and the normal contact of the 'recelving'relays. RW and RE in'series. The alternate contacts of the receivingrelays are connected to battery leads of the opposite sign to thatconnected with the point 16. The armature of the relay PW is arranged sothat when said relay is operated in response to the transmission of asignal from the loop the normal connection of battery over the contactof the receiving relays RlV and RE is opened and the normal batteryconnection is established directly over the armature of the relay PWindependently of either re-- ceiving relay.

urther details of the apparatus will be clear from the description ofthe operation, which is as follows: Normally, when s1gnals are nottransmitted, a carrier frequency incoming from the line MLE- passes.through the amplifier RAE and over the connection 13 to the'amplifierflAN, and thence to the" main line section MLW; similarly, a car rierfrequency passes from west to east from.

the main line section MLWthrou-gh the amplifienRAlY, over the circuit 12to the amplifier TAE, and thence to the main line sectioni MLE-. Signalsmay be transmitted in eitherqli'rection by interrupting the 'carrierfrequency transmitted in thedesired direction. Since the circuit isintended to operate on a half duplex basis, however, signalswill inpractice 'be transmitted over only one of the paths above described at atime. If signals'are transmitted over the first mentioned pathbyrinterrupting the carrier frequency,the detector DE will respond tothe interruptions, and the polarized relay RE will shift its armaturefrom negative battery to positive battery, "When the armature of therelay RE was connected to negative battery, since the other end of theloop was connected to positive battery, a current 'fiow through the loopwind; ings of the polar relays occurred which was twice'as great as: thecurrent flow passing through the balancing windings, which wereconnected directly to ground, The effect due to the current flow in theupper windings, therefore, predominates, and the pull asserted is insuch a direction as to hold the armatures of said relays in the normalposition. When the armature of.v the receiving relay RE is shifted topositive battery, however, the battery connections at the opposite endsof the loop are opposing,'consequently no'current flows through theloop, and the Sounders-included therein (not shown) release theirarmature-s. The upper windings of the polar relays PE, PW, and PW arealso deenergized, and current flows only through the lower windings ofsaid relays. The current flow is reversed, however, from that normallyflowing and consequently tends to hold the armatures of the relaysagainst their normal contact,- so that the transmitting relay PEh'is"ineifective to transmit the signalbackito the line MLE,

from which it came, and the relay PW-is ineffective toshort-circuit theconnection 13, over which the carrier signals Iare being transmittedfrom one line section to the other.

In a similar manner, if signals from the line MLW'are transmitted overthe conductor' 12 to the line section MLE by interrupting the normallytransmitted carrier frequency, the receiving relay RW responds andconnects positive battery to-the point 16, so that no current flowsthrough the loop and the sounders therein release their arma tures.Theeffect upon the polar relays PW and PW is the same as that alreadydescribed.

. If it is desired to transmit signals from the loop to the two linesections, the loop may 1 be interrupted by means of a sending keynotshown). Each time the loop is opened,

quencies normally transmitted from each line section to the other arediverted to ground, and thus interrupted so far as transmission to theother transmission line is concerned. The signals originating in theloop L will therefore be transmitted to each line sectionasinterruptions in the carrier frequency. The relay PW, in shifting itsarmature to its alternate contact, connects negative battery to thepoint 16 directly over said contact, and independently of the armaturesof the receiving relays RE and RW, so that said relays are ineffectiveto transmit si-gnalsto the loop while signals are being transmitted fromt e loop.

A break signal may be transmitted from the loop when signals are beingreceived from either line section by holding open the loop by means of asending key. The opening of the loop causes the closing of the shortcircuit connections 14 and 15 in the manner previously described, andtherefore the carrier frequency transmitted from each line section tothe other will be interrupted during the continuance of the breaksignal. The effect of the break signal at the sending station, which maybe assumed to be similar to that illustrated in Fig. 1, may be underbetransmitted over the through repeater stood from the eifect of a breaksignal received by the loop L. If a break signal comes in from the linesection ML'W,'the receiving relay RW shifts'its armature and connectspositive battery to the point 16. As soon as the armature of the relayPW assumes its normal position, which will occur when the loop is closedby the transmission of the space signal, no current flow occurs throughthe upper windings of the relays PE, PW and PW, and the current flowthrough the lower windings is in such a direction as to hold theirarmatures against their normal contacts. The operator, in opening andclosing the loop for further transmission of signals, will observe thatthe local sounder does not follow the sending key, and will therefore beapprised that a break signal has been received.

Fig. 2 illustrates a similar arrangement adapted to be operated upon afull duplex basis. The through repeater connections are the same as inFig. 1. In this instance,

however, signals wili in practice he simultaneously transmitted in bothdirections by interrupting the normally transmitted carrier frequency.This involves the provision of an additional subscribers loop, so thatsignals may be received and transmitted simultaneously from thesubscribers station. One of the loops is arranged to receive throughsignals transmitted from to that shown in Fig; 1, but in this instancethe normal battery connection to the point 16 extends onl over thecontact of the receiving relay W, and is entirely independ- 'ent of thereceiving relay RE. Polar relays PE'and PE are ascociated with the loopLE, said relays havingtheir upper windings in the loop and the lowerWHldings in the balancing circuit MNE. A connection extends fromthejunction point 17 of the polar relay windings over the normal contact ofthe armature of the polar relay PE, and over the normalcontact of thereceiving relayRE to negative battery. Positive battery is connected tothe alternate contact of the receiving relay RE,.and the connection issuch that when the armature of the polar relay PE is shifted from itsnormal position the battery connections controlled by the relay RE areopened, and an independent connection to negative battery is closed. a

The operation is as follows: Signals will channel from the line sectionMLE to the line section MLW as described in connec-- tion withFig. 1.Each time the frequency is interrupted the receiving relay RE respondandshifts its armature from negative battery to positive battery, so thatthe battery connections at each end of the loop LE are -mutuallyopposing. No current flows through the loop, therefore, and sounders inthe loop respond. The upper windings of the polar relays PE and PE aredeenergized' but the current flow through the lower windings isin such adirectionas to hold the armatures of said relays against their normalcontacts, and the signal is thereby prevented from being transmittedback to the line section MLE. Signals may be transmitted from the loopLE by opening and closing the same. Each time the loop is'opened. theupper windings of the relays PE and PE are deenergized, and the lowerwindings become effective to shift their armatures to their alternatecontacts. The armature of the relay PE, when shifted,closes'shortcircuit connections 14,

whereby the carrier frequently transmitted simultaneously.

from west to east over the circuit 12 may be interrupted, and signalstransmitted over the line sections MLE. The armature of,

the polar relay PE is shifted at the same time, and opens the batterycircuit controlled by the receiving relay RE, and connects the negativebattery to point '17 independent of the saidrelay. The receiving relayis therefore ineffective, to transmit signals to the loop when signalsare being sent from the loop.

The voperation of the lOOp 'withtre spect to receiving signalstransmitted from west to east and with respect to the trans-1 mission ofsignals from the loop west will l1c readily-understood from theoperations above. The details of this featureof the operation 'need not,therefore, be further considered.

It will .be seen from the description of Fig. 2 that While the carrierchannels are arranged to be operated full duplex, eachof the subscribersloops LE-and LW'is operated on a half duplex basis, as the same loop isused both for transmitting and receiving, the t wo operations cannottake place F igi'3i'l'li1strates an arrangement, how- ....e.y:er., inwhich not only the carrier channels i This involves the 'are'operatedfull duplex, but the loops are "also arranged to be operated fullduplex. provision of four loops, :the loop RLE receiving signalstransmitted from east to West, the loop RLW receiving signalstransmitted fromv west to east, the

loop TLE transmitting signals east, and the loop TLWV transmittingsignals west. As an additional feature, a switch SS is pro- Videdwhereby the transmitting loops 'TLE andTLW may be connected together,so. that'.si -gnals may be transmitted both eastand' west from the loopby operating a single key. The receiving relays RE and-RW are arrangedtomerely open and close the loops RLE and RUW respectively. In the normalarrangement of the 'loopsaTLE and arranged as indica edf balancing;circui TNE and T'NW are. pr0v.-ided for the two loops, said balancingcircuits being so arranged that, duetothe potential of the batteriesconnected to thejunctionpoints 16 and '17 of the loops andb'alancing'circuits, a greater current fiows through the loop than flowsthrough the balancing circuit. The windings of polar relays PE and PW iare arranged so that the upper windings are in the loop circuits and thelower wind- .the line section signals.

I the frequency transmitted exam 1e, the;

as Figs. 1 and 2. The battery connections to the points 16 and 17 are ofopposite signg'so that ifthe loops TLE and TLl/V be clearly connected bymeans of the switch SS, a greater current will flow through the serialloop thus obtained thanthrough the balancing circuits, due to the factthat the batteries arelseries aiding. With thecir- "cuit in thiscondition, signals may be simultaneously transmitted from the loopbothto the east and to the west by operating either the key KB or the keyKW.

The operation is as follows: transmitted .from the line section the-linesection MLlV through the repeater connection 13 willf'operate throughthe detector'D to respond, thereby opening and closing the" loop circuitRLE so that the receiving sounder ltSE records the signal. In a sim-.

ilar manner carriersi'gnals' transmitted from MLVV to the line sectionMLE .over the repeater connection 12 cause the receiving relay RW torespond, thereby opening and closing the loop so thatthe receivingsounder RSW records th With the switch SS in.normal position as shown inthe drawing, loop-s TLE and TLVVai'e both grounded and signalsmay besimultaneously nipulating keys KE the'loop TLE is opened, the upperWinding of the polar relay PE is deenergized, and the lower windingthereof becomes effeo-' tivetoshift its armature to close the shortcircuit ,conection 14, thereby interrupting over the conductor 12to theline section NLLW. Similarly, the opening of the loop the upper windingof the polar relay PW, so that the lower winding becomes effective toshift the armature of the relay and close the short circuit connection,15, thereby interrupting the carrier frequency normally transmitted overthe circuit 13 to the main line sectiOnMLWJ Signals MLE to E to causethe receiving relay RE inc sent from each'loop by'mav and KW. Eachtime-'- TLW deenergizes If the switchSS is shifted to connect the loopsTLE and TLW in series, signals may be simultaneously transmitted botheast and west by. the same key. If the serial loop thus formed;isope'ned by the key KE, for

lays E and are deenergized, and the upper windings of both re canarmature of both relays, thereby interrupting the normal carrierfrequency transmitted in each direction from one line section to theother. Consequently, the signals from the serial loop are transmitted tothe line section MLE as interruptions of the carrier frequencytransmitted from MLVV to MLE, while the similar interruptions of theloop are transmitted to the line MLW as in-' by theoscillator, and thisfrequency may be interrupted by the short circuit connections 14: and15, which will extend over a portion of the conductors 12 and 13 to thegrid circuits of the transmitting amplifiers. The operations of sendingand receiving with the circuits thus altered will be obvious from theoperations already described, and need not be further discussed;

It will be obvious .that the general principles herein described may beembodied in -many other organizations widely differentfrom thoseillustrated, without departing from the spirit of the invention as,defined in the following claims.

What is claimedis:

1. In a signaling system, two transmission line sections over whichcarrier currents may be transmitted, a carrie'rrepeater arrangement forinterconnecting said sections, said repeater arrangement comprisingcarrier transmitting channels and carrier receiving channels associatedwith each line section, means for interconnecting the carrier receivingchannel of each line section with the carrier transmitting channel ofthe opposite line section, a low frequency telegraph circuit, abalancing circuit therefor, a polar relay arrangement having windings insaid telegraph circuit and balancing circuit, means whereby said polarrelay may control the transmission of carrier.

currents from at least one of said carrier transmittting channels to thecorresponding line section, a receiving relay associatedwith at leastone of said carrier receiving channels, a source of current connected tothe junction point of the windings of said polar' relay arrangement overone contact of said receiving relay, a second source connected to theopposite end ofsaid telegraph circuit, said second source being so poledas to be mutually aiding with respect to said first source, a thirdsource connected to another contact of said receiving relay, said thirdsource being so poled that when the armature of the receiving relay isshifted,

mutually opposing sources will be connected to said telegraph circuit,and means whereby when said polar relay arrangement is opjerated inresponse to signals received over said telegraph circuit, said firstmentioned source will be connected to the junction pointof the windin sof said polar relay arrangement indepen' ently of said receiving relay.

2. In a signaling system, two transmission line sections over whichcarrier currents may be transmitted, a carrier repeater arrangement forinterconnecting the ends of said line sections, said carrier repeaterarrangement comprising carrier transmitting channels and carrierreceiving channels associated with each line section, means forinterconnecting the carrier receiving channel associated with each linesection with the carrier transmitting channel associated with theopposite line section, a low frequency telegraph circuit, a balancingcircuit there-.

for, a polar relay arrangement having windings in said telegraph circuitand said balancing circuit, said polar relay arrangement controlling thetransmission of. carrier currents from both transmitting channels to thecorresponding line sections, receiving relays associated with eachcarrier receiving channel, a source of current connected with thejunction point of the windings of said polar relay arrangement oyer-acontact of each of said receiving relays in series, a second source ofcurrent connected to the opposite end of said telegraph circuit, saidsecond source of curent being so poled as to be mutually aiding withrespect to said first source, and a third source connected to othercontacts of each of said receiving relays, said third source being sopoled that when the armature of either receiving relay is shifted,mutually opposed sources are connected to opposite ends of saidtelegraph circuit.

3. In a signaling system, two transmission line sections over whichcarrier currents may be transmitted, a carrier repeater arrangementforinterconnecting the ends, of said line sections, said carrier repeaterarrangement comprising carrier transmitting and carrier receivingchannels associated with each line section, means for connecting thecarrier receiving channel associated with each line section ith thecarrier transmitting channel associated with the opposite line section,a low frequency telegraph circuit, a balancing circuit therefor, a po arrelay arrangement having windings in said telegraph circuit and saidbalancing circuit,

said polar 'relay arrangement controlling.

- l tually' aiding with respect to said first source, and a third sourceconnected to other contacts of each of said receiving relays, said thirdsource being so poled that when the armature of either receiving relayis shifted, mutually. opposed sources are connected to opposite ends ofsaid telegraph circuit, and means controlled by said polar relayarrangement whereby said first mentioned source may be connected to thejunction point ofthe windings of said polar re-.

lay arrangement independently ofthe contacts of either receiving relay.

4. In a signaling system, two transmissionv line sections over whichcarrier currents may be transmitted, a carrier 1 repeater arran ementfor interconnecting the endsof said line sections, said repeaterarrangement comprising carrier transmitting channels and carrierreceiving channelsassoclated wlth each ,35 line section, means forinterconnecting the carrier receiving channel of eachline section withthe carriertransmitting channel of the opposite line section, a lowfrequency telegraph loop circuit, a pair of transmitting 4 polar relayseach having loop vwindings and balancing windings, fthe loop windingsbeing a q mutually in series in said loop circuit, sai polar relayscontrolling the transmission of carrier currentsfrom the transmittingchannels to the correspondin line sections, mu-

tually aiding sources 0 current connected to opposite ends of said loopcircuit, and means associated with said loop whereby both polartransmitting relays may be operated jointly to transmit signals fromsaid loop over both line sections simultaneously.

5. In a signaling system, a' pair of trans-' mission line sections overwhich carrier cur rents may be transmitted, a carrier repeater apparatusfor interconnecting the ends of said line sections, said repeaterapparatus comprising carrier transmittlng channels and carrier receivingchannels associated i with each-"line section, meansgfor interconnectingthe carrier receiving channel ofeach line section with the carriertransmitting channel of thenopposite line section, a low frequencytelegraph circuit, abalanclng circuit therefor, a pair of polar relayseach having windings in the telegraph circuit and 1n the balancingcircuit, thewindings of said polar relays in said telegraph circuitbeing mutually in series and the wind ings of said polar relays in'thebalancing circuit being mutually in series, means op 'erated by, atleast 'one of said polar relays for controlllng the transmission ofcarrier currents from one of said carrier transmitter channels to a linesection, a receiving relay associated with at least one of saidcarrierreceiving-channels, a source of current connected to the junctionpoint of the'windings of said polar relays over one contact of saidreceivingv relay, a second souroeof current connected to the oppositeend of'said telegraph circuit, said second source being so poled asto bemutually widing with respect to the first source, and a, third source,connected to another contact of saidreceiving relay,-said third sourcefi being, of opposite polarity from said first source, and meanscontrolled by one of said polar relays whereby when signals aretransmitted to the polar relays over said low freuency telegraphcircuit, said first nientloned source will'be connected to the junc- 9tion point] of the windings of said relays inde endently of saidreceiving relay.

n testimony whereof, I have signed my name to this specification this18th day of October, 1920. I I

" BAXilER r. HAMrLro-NQ

